The invention relates to an apparatus for positioning at least one component within an endoscopic system, comprising a hermetically tight housing, at least one external magnetically active element which is arranged outside the housing, and at least one internal magnetically active element which is arranged inside the housing, a magnetic force coupling acting through the housing between the external element and the internal element, it further being possible for the external element and the internal element to move at least with an axial movement component with reference to a longitudinal axis of the housing, and the internal element being in operational connection with the component in such a way that a movement of the internal element causes a movement of the component.
In the sense of the present invention, the term component comprises, for example, optical components, for example lenses with or without a mounting in an optical head of an endoscope. Such an optical component can be, for example, part of a focusing device of an endoscope for focusing the endoscopic image. However, mechanical components also come under the term of components.
In the sense of the present invention, endoscopic systems are understood as endoscopes, or else endoscopic camera systems.
In the sense of the present invention, a hermetically tight housing is understood as a housing sealed in such a way that it can be autoclaved, for example, without there being the risk that, in conjunction with the extreme temperature fluctuations, dampness or liquids, and therefore contaminations, can penetrate into the interior of the housing.
In the sense of the present invention, a magnetically active element is understood as a magnet, for example a permanent. magnet, or else an element or material which can be magnetized under the influence of a magnetic field, or else an electromagnet. Thus, for example, the at least one external magnetically active element can be a permanent magnet, and the at least one internal magnetically active element can be a magnetizable ferromagnetic material or element, or vice versa. It is sufficient if the at least one external magnetically active element or the at least one internal magnetically active element generates a magnetic field, and the respective other element then cooperates in a magnetically force-coupled fashion under the influence of this magnetic field with the element generating the magnetic field. The magnetic force coupling between the at least one external magnetically active element and the at least one internal magnetically active element acts in this case through the housing, as a result of which a so-called magnetic coupling is implemented.
From German Utility Model DE 88 10 044 U1, an apparatus for positioning at least one component within an endoscopic system is known having the at least one external magnetically active element arranged on the inside of an external ring arranged concentrically about the housing axis, and the at least one internal magnetically active element is guided in the form of an annular magnet inside the housing in a slideway, and is fixedly connected to the component to be positioned. The external ring, which carries the external magnetically active element, serves as an actuating element, and rotating the ring axially moves the ring, and thus the external magnetically active element, along a screw guide, as a result of which the internal magnetically active element is likewise moved axially. In this known apparatus, the external magnetically active element and the internal magnetically active element extend over the entire circumference about the longitudinal axis of the housing. Such an arrangement of these elements over the entire circumference can compensate the radial attractive force between the internal and external elements in such a way that the internal element is not pressed against a sliding seat subject to friction, something which would cause an increased frictional grip during the axial movement of the internal element, as a result of which the axial movement of the internal element, and thus of the component to be positioned, could not be performed without jerking. However, the arrangement of the external and internal elements over the entire circumference entails an increased outlay on costs for the apparatus. If the external magnetically active element and the internal magnetically active element were to extend only over a partial circumference of the housing of the apparatus, there would, by contrast, be the disadvantage that the radial attractive force between the elements would not be compensated for and this would lead in the case of a sliding guidance for the internal and/or external elements to increased friction during their movement, as a result of which it would be impossible to ensure positioning of the at least one component without jerking.
Another design of an apparatus for positioning components within endoscopic systems is disclosed in DE 197 13 276 A1, in the case of which a plurality of external magnetically active elements are arranged on an annular element arranged outside the housing concentrically with the housing axis, and a plurality of internal magnetically active elements are arranged on an annular element arranged inside the housing, likewise concentrically with the housing axis. Both the external annular element and the internal annular element are rotatable, but axially undisplaceable. In order by rotating the external annular element to achieve an axial movement of the at least one component to be positioned, the internal ring is mechanically connected to the component via a type of gear in the form of a helical groove in order to transmit the rotation of the external ring into a translatory movement of the component. The lead of the helical groove in this case determines the ratio between the rotational angle of the external annular element and the displacement travel of the component to be positioned. However, the lead cannot be selected arbitrarily, in particular it is bounded above because otherwise self-locking of the gear occurs. Particularly in the case of large leads of the helical groove, the friction can interfere in a jerky movement. Consequently in practice it is necessary to select the lead such that the external annular element must always be rotated by a relatively large angle in order to obtain a comparatively small translatory movement. However, this is disadvantageous in the case of apparatuses, for example focusing devices, in which large adjusting travels are to be quickly handled.
From U.S. Pat. No. 5,359,992 an apparatus for positioning components within endoscopic systems is known, in the case of which there are constructed diametrically opposite in an external annular element, which is arranged, in turn, concentrically with the housing axis and around the housing, two helical slots in which round magnets are inserted diametrically opposite one another. The round magnets engage into an axially extending cutout on the outside of a sleeve arranged in the ring. A rotation of the external ring therefore causes an axial displacement of the external magnet. Magnets situated diametrically opposite in a corresponding fashion are present in the internal sealed region and track the movements of the external magnet and thus effect the coupling. A disadvantage of this configuration is the areal slideway, heavily subject to friction, of the internal magnets and even here, also, of the external magnets.
The same problem exists in the case of the apparatus known from U.S. Pat. No. 5,056,902 for positioning components inside endoscopic systems, which serves there as a focusing device. In the above-named known apparatuses, in which both the external magnetically active element and the internal magnetically active element can be displaced at least with axial movement components, the disadvantages consist in a slideway which is subject to friction and has an areal bearing surface of the at least one internal magnetically active element, which bearing surface is heavily subject to friction because of the attraction between the external element and the internal element. However, because the slideway of the at least one internal magnetically active element inside the housing is subject to friction, jerky movements of the at least one component occur from time to time when it is being positioned, since the not inconsiderable static friction of the internal magnetically active element must be overcome at the start of each axial movement of the at least one external magnetically active element. Because of this, however, exact positioning of the at least one component is not always ensured.
In the case of the known apparatuses, the friction in the movement of the magnetically active elements can be reduced only by configuring the elements over the entire circumference, or at least by a rotationally symmetrical arrangement of the elements, and this in turn is associated with an increased outlay on construction.
It is therefore the object of the invention to improve an apparatus of the type mentioned at the beginning to the effect that, in conjunction with a design of low complexity, the magnetic coupling permits the at least one component to be positioned as far as possible without jerking.